The present invention relates generally to operations performed in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides a method of forming connections between tubular strings downhole.
It is common practice to use a packer or other anchoring device, such as a liner hanger, to secure a liner to a casing string downhole. However, the use of such anchoring devices unduly restricts access and fluid flow through the casing. In addition, these conventional anchoring devices are costly and sometimes difficult to set in certain circumstances.
Some anchoring devices, such as packers, also provide sealing between the liner and the casing. However, this sealing engagement requires a substantial amount of annular space between the liner and the casing, to accommodate the mechanical setting apparatus of a typical packer. Thus, the liner drift diameter must be substantially less than the casing drift diameter.
Furthermore, conventional anchoring devices cannot be used with expandable tubular strings, such as casings or liners which are expanded downhole. For example, a typical packer is not designed to be expanded outward along with the tubular string in which it is interconnected.
From the foregoing, it can be seen that it would be quite desirable to provide an improved method of forming connections between tubular strings downhole, which method overcomes some or all of the above described deficiencies in the art.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, a method is provided for connecting tubular strings downhole. The method does not require the use of packers or other anchoring devices, yet the method secures the tubular strings to each other and provides a seal between the tubular strings.
In one aspect of the invention, a method is provided which includes the steps of installing a first tubular string in a wellbore, conveying a second tubular string into the first tubular string and then crimping the tubular strings to each other. The step of crimping the tubular strings together may form a metal to metal seal between the tubular strings. Alternatively, a sealing material may be positioned between the tubular strings. The sealing material may be compressed between the tubular strings in the crimping step.
In another aspect of the invention, the first and second tubular strings may be bonded to each other downhole. For example, a bonding agent, such as an adhesive, may be used between the tubular strings. The bonding agent may also serve to seal between the tubular strings. The bonding agent may be compressed between the tubular strings in the crimping step.
In yet another aspect of the invention, the second tubular string may be displaced through a window formed through a sidewall of the first tubular string. The crimping step may be performed on a portion of the second tubular string which remains within the first tubular string. The crimping step may be performed on an end of the second tubular string positioned at the window. The crimping step may be performed on a portion of the second tubular string extending laterally across a longitudinal bore of the first tubular string.
In still another aspect of the invention, the second tubular string may be expanded within the first tubular string. The first tubular string may also be an expandable string. Preferably, the first and second tubular strings have substantially equal inner drift diameters after the connection is formed between the tubular strings.
These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of a representative embodiment of the invention hereinbelow and the accompanying drawings.